Scott (back) played catch in the outfield at Minute Maid Park on Tuesday, Brian McTaggart of MLB.com reports.
The Astros placed Scott on the 15-day injured list Saturday, retroactive to Sept. 18, due to a thoracic spine strain.
Scott will replace Jake Bloss as the starting pitcher for Monday's game against the Pirates, Brian McTaggart of MLB.com reports.
The Astros selected Scott's contract from Triple-A Sugar Land on Thursday, Brian McTaggart of MLB.com reports.
Scott signed a minor-league contract with the Astros on Dec. 12.
The Athletics outrighted Scott to Triple-A Las Vegas on Monday.
The Athletics optioned Scott to Triple-A Las Vegas on Tuesday.
Scott was recalled from Triple-A Las Vegas on Tuesday, Martin Gallegos of MLB.com reports.
Scott was optioned to Triple-A Las Vegas on Saturday.
Scott will start Tuesday's game against the Giants as Oakland's opener.